The present invention relates to a room temperature-curable organopolysiloxane composition or, more particularly, to a room temperature-curable organopolysiloxane composition capable of giving a cured elastomer having a low elastic modulus, which can be stored with stability under a hermetically sealed condition.
Various types of room temperature-curable organopolysiloxane compositions, referred to as RTV compositions hereinbelow, capable of giving a low-modulus elastomer by curing are known in the prior art, in which the organopolysiloxane component has aminoxy groups to serve as a crosslinking agent. For example, Japanese Patent Publication No. 42-24545 teaches a RTV composition comprising a silanolic hydroxy-terminated diorganopolysiloxane as the principal ingredient, a difunctional aminoxysilane and a trifunctional aminoxysilane. A problem in such a RTV composition is that the composition as a commercial product cannot be formulated in the form of a one package preparation because the composition is unstable even under a hermetically sealed condition. It is usual that the composition is prepared in the form of a two-package preparation and the contents of the separate packages are blended together directly before use to cause some inconveniences in respect of the workability therewith.
Japanese Patent Publication No. 52-30020 proposes an improvement of the above described RTV composition by replacing the difunctional and trifunctional aminoxysiloxanes with a difunctional amidosilane and trifunctional aminoxysiloxane, respectively. The RTV composition of this type is also accompanied by the disadvantages that a high boiling-point amide compound is produced as a by-product of the curing reaction to greatly decrease the adhesive bonding strength of the cured rubber composition to the substrate surface in addition to the still insufficient storage stability as a consequence of the formulation with an aminoxysilane as the trifunctional component. Furthermore, such a composition has been required to be improved to solve the problem that the undercoating layer on the substrate is subject to the attack of the RTV composition or the surface or a metallic substrate is subject to corrosion.